The antigenic determinants recognized by three monoclonal antibodies to keratan sulphate involve sulphated hepta‐ or larger oligosaccharides of the poly(N‐acetyllactosamine) series

Abstract

The carbohydrate determinants of keratan sulphate recognized by three monoclonal antibodies (5‐D‐4, 1‐B‐4 and MZ15) have been investigated by solid‐phase radioimmunoassay using bovine corneal keratan sulphate as the immobilized reference antigen. The antibodies appeared highly specific for sulphated poly(N‐acetyllactosamine) sequences, for their binding was strongly inhibited by preparations of keratan sulphate, but not by glycoproteins with non‐sulphated poly(N‐acetyllactosamine) sequences of I and i antigen types, a desulphated keratan sulphate hexasaccharide, an array of neutral and sulphated mono‐ and disaccharides and other glycosaminoglycans. Inhibition of binding assays using a series of structurally characterized sulphated di, tetra‐, hexa‐, octa‐ and decasaccharides, and partially characterized larger oligosaccharides, isolated from bovine corneal keratan sulphate after digestion with endo‐β‐galactosidase (see preceding two papers in this journal) showed that the smallest oligosaccharide reactive with all three antibodies was the linear pentasulphated hexasaccharide, E‐II although antibody 1‐B‐4 reacted with a tetrasulphated analogue. The heptasulphated octasaccharide, G‐III, was more active; among the structurally characterized keratan sulphate oligosaccharides the nonasulphated decasaccharide, I‐IV, was the most active. Thus, the hepta‐ and octasaccharide sequences, indicated by brackets below are proposed as candidate antigenic structures recognized by the three monoclonal antibodies. (Formula Presented.) Antibody 5‐D‐4 differs from the other two antibodies in reacting relatively strongly with a minor oligosaccharide which chromatographs as a hexasulphated octasaccharide, G‐I, and most strongly with a minor sulphated, linear dodecasaccharide, J‐II, which has been partially characterized [Tang, P. W., Scudder, P., Mehmet, H., Hounsell, E. F. & Feizi, T., unpublished results] and may contain N‐sulphated glucosamine residues. Copyright © 1986, Wiley Blackwell. All rights reserved